This invention relates generally to directional control devices for winches and, more particularly, to a mechanical limit device for adjustably halting the operation of a winch at a preset point in the machine cycle.
A mechanical limit device can be generally described as a device that halts the operation of a machine at a preset point in the machine's cycle and prevents further operation until the device is reset by some action. A device of this type is often used on a winch to limit the raising and lowering point extent of a load. Once the limit has been reached, the operator would normally be required to reverse the winch for a certain distance in order to reset the device.
Two common types of mechanical device in current use today are either rotary or linear devices driven through gear reduction by the machine. Rotary devices are geared to track the movement of the machine in less than one revolution of a cam which is used to activate a switch to turn off the machine. Similarly, a linear device is geared to track the movement of the machine by employing a threaded nut traveling along a lead screw to activate a switch. The closer the tracking movement is to the movement of the machine, the greater will be the accuracy of the device and this determines the exact stopping point at each preset limit and the minimum operating distance between the limits. For increased tracking movement, it is desirable to make the cam in a rotary device as large a diameter as possible and the lead screw in a linear device as long as possible. Rotary devices are generally preferred since they will continue to rotate beyond one revolution should the switch fail to stop the machine as intended. If the switch on a linear device should fail to stop the machine, the traveling nut will eventually reach the end of the lead screw. At this point it must disengage to avoid damage to the components. Once disengaged, it will require retiming before it can function again.
The foregoing illustrates limitations known to exist in present devices and methods. Thus, it is apparent that, it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.